Process fob preparing substituted



Patented Dec. 2, 1941 "UNITED. STATES PATENT, OFFICE PROCESS FOR PREPARING SUBSTITUTED PHTHALIC ANHYDRIDES Ernst Bergmann, Rehovoth, Palestine, ass fl or to Compagnie de Produits Chimiques et Electrometallurgiques Alais Froges et Camargue, Paris, France, a corporation of France No Drawing. Application January 17, 1940, se-- rial No. 314,355. In France January 26, 1939 4 Claims. (o1. zoo-s41) Phthalic anhydrides which are very valuable raw materials for obtaining polycyclic dyes, may be prepared advantageously'by using dlenic synthesis in two stages. The first stage comprises a combination between a diene and maleic anhydride, the second stage a dehydrogenation of the primary product or hydro-aromatic character.

in the case oi,-the product formed from 1,4-diphenylbutadlen'e and maleic anhydride for example, prior investigators were quite unable to succeed in preparing the corresponding phthalican hydride. a

According to the present invention, phthalic anhydrides can be particularly easily produced in a single reaction, by carrying out the condensation in nitrobenzene or another nitrated aromatic substance which not only acts as a diluent, but also as a dehydrogenating agent by reducing itself and giving the corresponding amine.

The reaction may be eilected with a diene or other appropriate unsaturated hydrocarbon such as a-vinyl-naphthalene, i. e.,' an hydrocarbon containing at least two conjugated double bonds.

Example 1 ,20 parts or lA-diphenylbutadiene, 10 parts'oi maleic anhydride and 15 partsoi nitrobenzene are raised to a temperature of 200 C. for 3 hours. When the mixture is cooled, the liquid sets throughout and the 3,6-diphenyiphthalic anhydride formed is filtered and, it necessary, recrystallized in methyl-ethyl-lretone'or in xylene.

'It forms colourless needles, with a melting point of 224' C.

it is converted, into 2-ben'zoyl 3,0-dipheny1-benzoic acid, melting point 167 C. whichis cyclized, by the known methods, into 1,4-diphenyl-anthraquinone. Similarly, the anhydride can be converted with the a-naphthols 'in the presence of boron oxide, into ketonic acids and then into oxynaphthacene-quinones, and it may be subjected to'other characteristic reactions or unsubstituted phthalic anhydride.

. Eaample 2 I By heating in the same manner, in nitrobenzene parts) l-phenylbutadiene (13 parts) and maleic anhydride parts) the anhydride of 3- phenylphthalic acid was obtained with an emciency of 80%. It boils under a pressure or 2 millimetres at 190 C. and it can be advantageously recrystallized in benzene. Melting point 143 C.

I Example 3 a-vinyl-naphthalene (15 parts) and maleic anhvdride parts) were heated in o-nitrotoluene (15 parts) for 2 hours at a temperature of 200 C. On cooling, the anhydride'ot phenanthrene- By treating with phenyl magnesiinn bromide,

1,2-dicarbonic acid crystallized. After recrystallization in acetic anhydride, it has a melting point of 311 to 312 C.

I claim:

1. A process for preparing substituted phthalic anhydrides, which comprises the step or ,reacting an hydrocarbon, containing at least two conjugated double bonds, with maleic anhydride, in

a nitrated compound which iunctions as hydrogen acceptorimder the reaction conditions.

2. A process for preparing substituted phthalic anhydrides, which comprises the step of reacting a diene hydrocarbon with maleic anhydride, in a nitrated compound which nmctions as hydrogen acceptor under the reaction conditions.

3. A process for preparing substituted'phthalic anhydrides, which comprises reacting an hydrobonds, with maleic anhydride, in nitro-benzene.

4. A process for preparing substituted phthalic' maleic anhydride, in 

